Merge branch 'master' into master

pipenv/core.py

@@ -2523,12 +2523,12 @@ def do_clean(
     # Ensure that virtualenv is available.
     ensure_project(three=three, python=python, validate=False)
     ensure_lockfile()
-    installed_packages = delegator.run(
+    installed_packages = filter(None, delegator.run(
         '{0} freeze'.format(which('pip'))
     ).out.strip(
     ).split(
         '\n'
-    )
+    ))
     installed_package_names = []
     for installed in installed_packages:
         r = get_requirement(installed)

tests/test_pipenv.py

@@ -1051,3 +1051,9 @@ requests = "==2.14.0"
             assert target_package in p.pipfile['packages']
             assert p.pipfile['packages'][target_package] == '*'
             assert target_package in p.lockfile['default']
+
+    @pytest.mark.clean
+    def test_clean_on_empty_venv(self, pypi):
+        with PipenvInstance(pypi=pypi) as p:
+            c = p.pipenv('clean')
+            assert c.return_code == 0